ARACHNIDA. 131 
Argentine and Chili. In the Old World their nearest allies, few in number, are 
found in West Africa and the Mediterranean. 
Tentative explanations of these facts may be illustrated by one or two cases. If the 
groups to which Chorizops and Pachylomerus belong are North American in origin, 
they may have extended thence southwards into Central America and northwards into 
eastern Asia. Pachylomerus, in addition, may have passed eastwards from America to 
Spain and Algeria, or its apparent restriction in the Old World at the present time 
to such widely sundered areas as the south-western Mediterranean and eastern Asia 
may be attributed to its former extension over Eurasia and its survival only in those 
two localities. Against this hypothesis can only be urged the impossibility of assigning 
any cause for its extinction in other parts of the Asiatic district. 
If the group to which Actinopus and LEucteniza belong was evolved in South 
America, these genera may have moved northwards into Central America; and the 
restriction of an allied genus to Australia may be assigned to the entry of the group 
into that country from South America. | 
Since tropical America is the headquarters of [schnothele, judging from the number 
of indigenous species, it may be provisionally regarded as the original home of the 
genus. Thence it may have passed by a transatlantic bridge to Africa, and so to 
Madagascar and India. 
These four genera of Mygalomorphe, apart from others which might have been 
cited, supply evidence, such as it is, for direct land-continuity, under tropical or 
warm temperate conditions, between (1) North America and eastern Asia; (2) North, 
Central, or South America and the Mediterranean ; (3) South America and tropical 
Africa; (4) South America and Australia. 
Corroborative evidence for “Antarctica” is supplied by another family (or sub- 
family) of Mygalomorphe, namely the Migide, which is related to the Ctenizide, 
but does not occur in Central America. It contains eight genera, distributed as 
follows :—Moggridgea and Pecilomigas, South and South-east Africa; yrtale, 
Micromesomma, and Thyropeus, Madagascar ; Heteromigas, Tasmania; Migas, New 
Zealand; and Calathotarsus, Chili. 
It appears to me to be impossible to assign any reason for the extermination of this 
group of Spiders in the northern portions of the continents to which they are now 
restricted, if the genera in question are the descendants of a family evolved sufficiently 
far to the north to have passed from the Old to the New World, or vice versd, along a 
North Atlantic or North Pacific route. | 
Turning to the Arachnomorphe, one or two of the Central American families may 
be selected to illustrate the restricted range of some and the wide range of others. 
The Senoculide and Acanthoctenide, each represented by a single genus, are 
peculiar to America, ranging from South America northwards to Mexico. ‘The 
Psechride are represented by two genera, Psechrus and Fecenia, in the southern and 
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